Power output of an internal combustion engine may be increased via increasing an actual total number of cylinders of the engine. The engine's increased displacement may allow the engine to consume more fuel so that engine power output may be increased. However, increasing the engine's displacement may increase engine pumping losses and engine friction. Further, depending on vehicle mass and driver demands, the engine may operate at higher loads for only a small fraction of engine operating time. Consequently, it may not always be desirable to increase an actual total number of cylinders.
One way to provide greater displacement and increased engine power output with reduced engine pumping losses at lower engine torque demands is to selectively deactivate engine cylinders. The engine cylinders may be selectively deactivated by closing intake and exhaust valves of the deactivated cylinder over a plurality of engine cycles while the engine continues to turn and provide positive torque to a vehicle driveline. The intake and exhaust valves may be deactivated via deactivating valve operators for each valve. However, deactivating valve operators can increase engine cost since deactivating valve operators are more complex than non-deactivating valve operators. Thus, deactivating intake and exhaust valves of a cylinder may not be as cost effective as is desired.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine system, comprising: an engine including a first cylinder with a first intake valve and a first exhaust valve, the engine including a second cylinder with a second intake valve and a second exhaust valve; a camshaft in mechanical communication with the first intake valve via a first deactivating valve operator; and a first non-deactivating valve operator providing mechanical communication between the first exhaust valve and the camshaft.
By deactivating a cylinder via a deactivating intake valve operator and without a deactivating exhaust valve operator, it may be possible to provide the benefits of cylinder deactivation at lower cost. In particular, since a deactivated cylinder includes non-deactivating exhaust valve operators, cost of deactivating a cylinder may be reduced nearly in half. Deactivating intake valves via the deactivating intake valve operator causes intake valves to be held in a closed position without opening over one or more engine cycles, thereby ceasing air flow through the deactivated cylinder. The exhaust valves of the deactivated cylinder continue to open and close over the one or more engine cycles since the valve operators acting on the exhaust valves are non-deactivating. Additionally, fuel flow to the deactivated cylinder is ceased as part of the cylinder deactivation procedure.
Engine pumping losses may be reduced when a deactivated cylinder's intake valves are held closed over an engine cycle while the cylinder's exhaust valves open and close over the engine cycle. Specifically, engine intake manifold pressure may be increased in response to deactivating one or more engine cylinders so that air flow through active cylinders compensates for the lack of air flow through deactivated cylinders. Increasing the engine intake manifold pressure may reduce engine pumping losses since less engine work may be lost to create vacuum in the engine intake manifold.
The present description may provide several advantages. For example, the approach may reduce vehicle system cost. Further, the approach may provide the benefits of cylinder deactivation such as lower engine pumping work. Further still, the approach may improve reliability of cylinder deactivation since fewer deactivating valve operators are used to deactivate a cylinder.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.